RAW: Elevated levels of metals found at the Mill City Stamp Mill

Elevated levels of mercury, lead, and arsenic have been detected during preliminary sampling of soils and historic mill tailings at the Mill City Stamp Mill, according to the Inyo National Forest.

In 2012, CalTrout received a grant from the Lahontan Regional Quality Control Board to monitor water quality in Mammoth Creek, according to a news release from the forest.

Monitoring included mercury, manganese, and others. The study conducted by CalTrout in 2012-2013 showed elevated levels of mercury in Mammoth Creek and that concentrations were the highest near the Mill City Stamp Mill. Based on the CalTrout study, the US Forest Service conducted the preliminary site sampling near the Stamp Mill in 2013.

The US Forest Service preliminary sampling at the Stamp Mill showed elevated levels of mercury, lead and arsenic in the soil and historic mill tailings. The detected levels of arsenic, lead and mercury in the preliminary sampling indicate that there is a potential risk to site visitors and nearby residents. Additional sampling is required to fully delineate the nature and extent of contamination that may be present as a result of historic mining activities at the site.

The US Forest Service will be conducting a Site Investigation this spring and summer to determine the full nature and extent of contamination and to better assess the degree of risk to recreational visitors, nearby residents, and to the environment and what actions may be needed to mitigate these risks.

“While we do not know the nature or extent of mercury contamination, we want to share the information we currently have with residents and visitors to the area,” said Ed Armenta, Forest Supervisor.